Ahmad Rahami
Ahmad RahamiReuters

The suspect in the bombing this month in New York's Chelsea neighborhood appears to have acted on his own, the FBI said Tuesday, according to AFP.

"We see so far no indication of a larger cell or the threat of related attacks," FBI director James Comey was quoted as having said during a testimony at a Senate committee hearing.

The suspect in the September 17 bombing that left 31 people wounded, Ahmad Khan Rahami, was arrested in New Jersey two days after the attack.

Rahami, who was wounded in a shootout with police, has been charged with four counts including use of weapons of mass destruction and bombing a place of public use.

He has remained hospitalized and is unable to appear before a judge, the New Jersey prosecutor's office said Tuesday.

In addition to the New York attack, he is charged with a pipe bombing, also on September 17, in Seaside Park, New Jersey, and planting several other bombs.

A naturalized U.S. citizen born in Afghanistan, Rahami, 28, made several trips in recent years to Afghanistan and Pakistan.

The terror charges came after the FBI admitted it had investigated Rahami for terrorism in 2014 following a complaint from his father, but found no link to radicalization or extremist sympathies.

Comey said Tuesday the FBI is seeing a slight slowdown in new U.S. terror investigation cases, but some 1,000 probes are currently ongoing.

"I hope that it's going to... head downward but it has not headed downward yet," he told the Senate Homeland Security and Governmental Affairs Committee.

By contrast, he said, the number of people leaving the country to join the Islamic State (ISIS) group in Syria or Iraq has fallen sharply.

"Where we used to see eight or 10 people from the United States trying to go to the so-called caliphate, we're now down to one or none a month," he said, according to AFP.

Hours after Rahami’s bombs exploded in New Jersey and New York, a stabbing attack took place in a mall in Minnesota, but it appears to have no connection to Rahami’s actions.

The Minnesota attack was claimed by ISIS, but local police have not found any evidence connecting the attacker to organized extremist groups.