Mumbai:  Six months after Mumbai was rocked by three coordinated blasts leaving 27 people dead, Maharashtra ATS on Monday claimed to have made a breakthrough with the arrest of two alleged Indian Mujahideen operatives but the mastermind and planters of the bombs are still at large.

Naqi Ahmed Wasi Ahmed Sheikh and Nadeem Akhtar Ashfaq Sheikh, originally from Bihar's Darbhanga district, were arrested even as a manhunt continues for top IM leader Yasin Bhatkal.

"Naqi Ahmed Wasi Ahmed Sheikh (22) and Nadeem Akhtar Ashfaq Sheikh (23), who are already in police custody in connection with a forgery case, have been arrested today in the blasts case," ATS chief Rakesh Maria told reporters.

Naqi and Nadeem, residents of Madanpura and Antop Hill areas in the city, were earlier arrested in connection with a case relating to procurement of SIM cards using fake documents. Six others including one Haroon Rashid Naik from Mumbra near Mumbai, whose remand has been sought, had also been held in connection with fraudulent procurement of SIM cards over a period of time since August 2011, Maria said.

"After Haroon's remand in granted, he will be arrested in the blasts case," Maria said, adding help extended by the underworld in commission of the crime had also emerged. He said around Rs 10 lakh received through Hawala channels was used in the crime but did not disclose the source from where the money came lest it would hamper investigations.

Maintaining that Naqi was indoctrinated by Bhatkal, Maria said it was he who helped the IM mastermind to rent the third floor apartment in Habib Building at Byculla last year.

Two-three apartments were rejected before finalising the Habib building quarters and Naqi paid for it, he said.

Maria rubbished claims by Naqi's relatives that he was innocent, saying he had been in touch with Bhatkal since 2008 and even visited his place in Bihar and that he was fully aware of the latter's antecedents. "We have evidence to corroborate this," Maria said.

Naqi and Nadeem were produced before a court which remanded them in ATS custody till February 2.

The ATS sought their custody saying they wanted to find out from where did the explosives for the blast come.

"The explosives were brought to Mumbai from Delhi by train but how they reached the national capital and from where is yet to be ascertained," said an ATS officer.

The third accused Haroon will be produced in the court tomorrow when he would be arrested in the blasts case.

"The accused have been charged under Unlawful Activities Prevention Act, Explosives Act, and sections of Indian Penal Code (IPC)," said an ATS officer.

Outside the court, Naqi's uncle Manzar said he had faith in the judiciary and that his nephew's innocence will be proved.

Maria said after the accused started staying in the rented apartment, the two of those still wanted along with Naqi enrolled in a gym in south Mumbai and also recede the sites to be targeted.

Though Maria refused to part with the names of the two wanted accused and described them only as 'A' and 'B' as revealing those could compromise the investigation, there have been reports in the media that they could be from Pakistan.

According to ATS sources, though Bhatkal and the other two whose names were withheld appeared to be the only wanted accused so far, their numbers could go up as the probe progresses.

Subsequently, Maria said, Nadeem was called to Delhi by Bhatkal and handed over a cloth packet containing the explosive and detonators used in the blast. "The explosives were brought by train," Maria added.

As per the instructions of Bhatkal, Naqi and Nadeem had stolen two Activa scooters a day before the blasts and explosives are fitted in them for explosions in Zaveri Bazaar and Opera House, said Additional Police Commissioner Sukhvinder Singh.

Did Maharashtra ATS allow bombers to slip away?

By declaring the arrest of Naqee Ahmed on Monday in last year's serial blasts in Mumbai, security agencies in the national capital feel that the Maharashtra ATS may be attempting to cover its tracks after the bombers involved slipped out.

Though Maharashtra ATS Chief Rakesh Maria was candid enough in admitting "competition" within various police forces in solving blast cases, officials at Union Home Ministry remained baffled as the announcement of arrest of 23-year-old Ahmed was flashed on television sets.

For the elite Special Cell of Delhi Police and special squad of Intelligence Bureau, Ahmed was the person who provided them with crucial leads in identifying Waqas and Tabrez, the two bombers in the 13/7 blast that left 27 people dead.

According to the officials, Ahmed was in Mumbai only to help in tracking down two bombers and the highly-secretive operation was being monitored by the top echelons of the security establishment closely from Delhi.

Ahmed was in the megapolis with undercover sleuths to help nab the two bombers, whom the Anti Terrorism Squad(ATS) Chief on Monday identified as suspect A and suspect B.

Naquee's submissions to the ATS form a part of statement that he had given to Delhi Police Special Cell.

In the national capital, his elder brother Taquee is moving from pillar to post to seek help for his brother.

"He has been helping the police only. Has this been heard before that a person is behind bars for being an informer of another police force. I think we are a democratic country," Taquee said, as tears rolled down his cheeks.

In Mumbai court, Naquee's counsel Khalid Azmi was reportedly disallowed from meeting his client.

Maria said while Bhatkal and two others, who had planted the explosives and whose names he refused to divulge lest it would hamper investigations, were eluding the police dragnet, another accused in the case--Haroon Rashid Naik—had already been arrested by ATS in a counterfeit currency case.

Naik, he said, had been arrested in August last year and ATS would today seek a transfer warrant for him from the court. "We need the custody of Naik from Mumbra for investigation of economic trail and conspiracy in the case," he said.

Maria trashed media reports that Bhatkal was in the city for several months after the blasts and that he was to visit the landlady of the Byculla apartment when he got the whiff of impending action by Mumbai police due to lack of coordination between Delhi police's special cell and Maharashtra ATS and escaped.

"Bhatkal was in the city in June and for some time in July. He left on July 13 and did not come back," he said.

The ATS chief said several articles including computer and clothes of the inmates of the Byculla room have been seized for forensic examination. "We have asked for a forensic analysis of the room as we believe that the IEDs used for the blasts were assembled in the room," he said.

Maria said 40 officers and over 100 men of the ATS had visited 18 states as part of the ongoing investigation and examined 12,373 witnesses.

The ATS chief also junked reports about any tiff or lack of coordination with Delhi police in carrying out the probe, saying investigators from Mumbai were getting all cooperation from their Delhi counterparts.

"Competition is good and it should be there. Which police will not want to crack the case, but there is no rivalry," he said.