Attorneys for an American jailed for more than four years in Yemen allege that their client has disappeared within Yemen’s maze of security facilities and is in danger.

Sharif Mobley, now 30, was snatched off the street by Yemeni security agents in 2010, after his contact with an American-born radical preacher had attracted the attention of U.S. counterterrorism authorities.

Mobley has not been seen by his attorneys or their representatives since late February. An April 2 court hearing that his attorneys expected would include an account of U.S. interest in Mobley leading up to his arrest was canceled because of a judicial strike, according to the British-based human rights group Reprieve.

Yemeni authorities have given conflicting and erroneous accounts of his whereabouts, Reprieve lawyer Cori Crider wrote in a letter last week to the U.S. Embassy in Sanaa.

“I request urgent action” to locate Mobley and assure his family and lawyers that he is safe, Crider wrote.

Mobley was jailed on allegations of killing a hospital security guard while trying to escape from detention weeks after his 2010 arrest. Yemeni authorities said that he tricked a guard into unshackling him, then grabbed a gun and tried to shoot his way out of the hospital where he had been taken for treatment of injuries received during his initial capture. He was again injured and recaptured during a gun battle with police.

His attorneys say he had suffered abusive interrogation by U.S. officials prior to the hospital attack and that he feared for his and his family’s lives. They challenge his initial seizure as an unlawful “kidnapping.”

Mobley was a New Jersey Muslim who grew increasingly devout and moved to Yemen with his young family in 2008 for what he said was religious and language education. U.S. officials have said they suspect he had extremist motives, and cite his contact with extremist preacher Anwar al-Awlaki, who was killed by a U.S. drone strike in 2011.

Mohammed Albasha, spokesman for the Yemeni Embassy in Washington, said Mobley is in the central Sanaa Correctional Facility.

But Crider insisted to U.S. authorities that Mobley is not in that prison, nor in another one where her representatives were directed last month.

“We have not had any news of him for 39 days, despite strenuous attempts to locate him,” Crider wrote last week. “We are extremely concerned as to Mr. Mobley’s safety and well-being.”

The State Department declined to comment on Mobley, citing privacy laws.

But Mobley’s attorneys are exempt from the privacy restriction, and they say that U.S. Embassy officials are similarly in the dark about Mobley’s whereabouts.

“We have contacted all the possible locations where he could be held. We have received denials from everyone except the Ministry of the Interior who said they would get back to us,” Reprieve quoted a U.S. Embassy official as writing last week.

Reprieve did not identify the official.