The U.S. said in a May 12 letter unsealed yesterday that Shahzad, 30, was interrogated after his May 3 arrest and advised daily of his constitutional rights to remain silent and to be brought before a judge. He repeatedly waived those rights and his right to an attorney, prosecutors in the office of Manhattan U.S. Attorney Preet Bharara said in the letter to two judges.

Law enforcement officials “are vigorously and expeditiously pursuing leads and other information provided by the defendant,” prosecutors said. The unsealed letter was described as a “report on the status of the case” and several portions of it were redacted by the government.

Shahzad was charged in a criminal complaint unsealed May 4 with one count each of attempted terrorism; attempted use of a weapon of mass destruction; using a destructive device in connection with an attempted crime of violence; transporting explosives; and attempting to destroy property with fire and explosives.

He was ordered held without bail after his first court appearance on May 18. At that hearing, Assistant U.S. Attorney Randall Jackson said the daily questioning had continued and that each day Shahzad had waived his rights.

‘Uninterrupted Access’

Prosecutors said that leads developed in the case have been pursued by “hundreds of agents in different cities working around the clock since the defendant’s arrest.”

“Uninterrupted access to the defendant has been, and continues to be, critical to this process, which requires, among other things, an ability to promptly verify with him the accuracy of information developed in the investigation,” according to the letter.

The letter to U.S. District Judge Loretta Preska, chief judge of the federal court in Manhattan, and George Yanthis, the court’s chief magistrate judge, was signed by Jackson and assistant U.S. attorneys Brendan McGuire, Jeffrey Brown and John Cronan.

Julia Gatto, a court appointed lawyer for Shahzad, didn’t immediately return a voice-mail message seeking comment yesterday.

‘Kill and Maim’

Shahzad, who was charged with trying to “kill and maim,” drove a Nissan Pathfinder carrying an improvised bomb made of firecrackers, propane tanks and gasoline canisters into the crowded Manhattan crossroads, prosecutors said in the complaint against him. The Pathfinder was found abandoned and smoking on the street as the items in the back smoldered, the U.S. said in court papers.

Attorney General Eric Holder said in a May 9 interview that Shahzad, a Pakistan-born naturalized U.S. citizen, was funded and directed by a Taliban group based in Pakistan. Authorities said the plot dated back to December.

Shahzad, who lived in Bridgeport, Connecticut, faces as long as life in prison if convicted.

Federal agents tracking the funding for Shahzad’s plot arrested three people on immigration charges in a series of raids across the northeastern U.S. on May 13.

The searches were “the product of evidence that has been gathered in the investigation since the attempted Times Square bombing” and didn’t relate to any known new threat, Holder said.

Suspect’s Number

Aftab Khan, a Pakistani man arrested in Massachusetts during the investigation into the failed Times Square bombing had Shahzad’s phone number and first name in his cell phone and written on an envelope, a government attorney said at a hearing yesterday in Boston, the Associated Press reported.

Khan, a gas station attendant, had the items in his belongings in his Watertown, Massachusetts, apartment, said Richard Neville, deputy chief counsel for U.S. Immigration and Customs Enforcement in Boston, the AP said.

Neville disclosed the information in court yesterday while trying to persuade an immigration judge to keep Khan in the U.S. Khan and two other Pakistani men arrested May 13 were ordered held on immigration charges and haven’t been charged criminally, the AP said.

The case is U.S. v. Shahzad, 10-00928, U.S. District Court, Southern District of New York (Manhattan).

--With assistance from Peter S. Green in New York and Tom Moroney in Boston. Editors: Michael Hytha, Fred Strasser.

To contact the reporter on this story: Patricia Hurtado in New York at pathurtado@bloomberg.net.

To contact the editor responsible for this story: David E. Rovella at drovella@bloomberg.net.