The officer identified the man as a 43-year-old from the eastern Indian state of Bihar. Anti-terrorist police raided his apartment in Katmandu on Saturday, he said.

“He was arrested on suspicion of his links with the Mumbai blasts,” he added, explaining that police were probing text messages and phone calls to someone in the Indian city.

It would be the first arrest anywhere in connection with the Mumbai explosions, the first attack on the city since the traumatic November 2008 assault by militants that left 166 dead and more than 300 injured.

Nepal police spokesman Nawaraj Dhakal confirmed an Indian man had been detained but denied it was related to the Mumbai blasts.

The police source, who said he took part in the operation to arrest the suspect, stood by his account and suggested senior officers wanted to downplay the detention while an investigation was underway.

The state-run Nepalese newspaper Gorkhapatra and Indian television channel CNN-IBN also reported Tuesday that an Indian man had been arrested on suspicion of being involved in the Mumbai blasts.

No one was immediately available for comment at Mumbai police.

The development, if confirmed, would provide valuable clues to police in India’s commercial capital who have struggled with the case despite the deployment of forensic teams and top detectives.

Anti-terrorism squad officers fear that monsoon rains which lashed Mumbai on the night of the attacks and for days afterward may have hindered the search for vital clues. Police have said the three rush-hour bombs contained ammonium nitrate and were set off by timer devices.

Teams of intelligence officers have fanned out nationwide to interview members of the Indian Mujahideen, a homegrown miliant group suspected of being behind the blasts.

Two suspected members arrested in Mumbai earlier this month in connection with bombings in the western city of Ahmedabad in 2008 have been questioned, police have said, as have people with known links to the criminal underworld.

The Indian Mujahideen claimed responsibility for the Ahmedabad attacks and a series of blasts across the country that year, including in the capital New Delhi.

The prime suspect in the Mumbai attack — the Indian Mujahedeen — has re-emerged three years after authorities believed they virtually wiped out the terror group in a crackdown that left many of its leaders dead, in jail or hiding abroad.

The return of the extremist network could herald a new wave of terror attacks across the country after three years of relative calm and threaten the recently renewed peace process with Islamabad.

Police said the Mumbai bombs, fabricated from ammonium nitrate, were similar to those used by the Indian Mujahedeen in the past, leading police to focus on the group.

“It is one of the most likely targets for us,” said Deven Bharti, a Mumbai police official.

The Indian Mujahedeen was not destroyed, said Ajit Doval, the former head of India’s Intelligence Bureau. “It was reorganizing itself,” he said.

The Indian Mujahedeen, which sprang out of the banned Students’ Islamic Movement of India, is “a radical fringe of technically-savvy disaffected Indian Muslims who embrace extremism in response to perceived injustices by the Hindu majority,” according to a 2008 diplomatic cable from the US Embassy in New Delhi obtained by WikiLeaks.

The youth were galvanized by Hindu extremists’ 1992 destruction of the 16th century Babri Mosque — and the bloody riots that followed — as well as a 2002 spasm of communal violence in the western state of Gujarat that killed more than 1,000 people, most of them Muslim.