Sources: Bombing suspects had originally planned for July 4 attack

Updated 7:27 PM ET

The suspected bombers in the Boston Marathon attack had originally intended for the plot to happen on July 4th, CBS News has learned.

According to CBS News correspondent John Miller, a U.S. official confirmed that detained suspect Dzhokhar Tsarnaev told authorities that the bombing was supposed to take place on the Fourth of July. The actual attack took place on April 15.

The official also said that Tsarnaev revealed that the bombs were constructed at his older brother Tamerlan's residence and that Tamerlan had brought Dzhokhar into the plot a couple of months before.

The official noted that Dzhokhar Tsarnaev had said different things at different times and that it is all subject to investigation.

In other news, the body of Tamerlan Tsarnaev has been claimed. Massachusetts Department of Public Safety spokesman Terrel Harris says a funeral home retained by Tsarnaev's family picked up his body Thursday. He has no more information.

The medical examiner determined Tsarnaev's cause of death Monday, but officials said it won't become public until his remains are released and a death certificate is filed. It was unclear on Thursday evening whether the death certificate had been filed.

Tsarnaev's widow, Katherine Russell, who lives in Rhode Island, learned this week that the medical examiner was ready to release his body and wanted it released to his side of the family, her attorney Amato DeLuca said days ago.

• Renowned defense lawyer to fight for Tsarnaev's life
• Feds: Boston bomber's friends hid incriminating evidence
• How Tsarnaev's friends may impact bombing case

"Of course, family members will take possession of the body," uncle Ruslan Tsarni of Montgomery Village, Md., told The Associated Press Tuesday. "We'll do it. We will do it. A family is a family."

He would not elaborate at the time. Tsarnaev's parents are still in Russia, but he has other relatives on his side of the family in the U.S., including Tsarni.

Tsarnaev died after a gunfight with authorities days after the April 15 bombing. The bombing, near the marathon's finish line, killed three people and injured more than 260 others.

Authorities said Tsarnaev and his younger brother got into a gunfight with police following a massive manhunt for them, setting off a pressure cooker bomb and tossing grenades before the older brother ran of ammunition.

Police said they tackled the older brother and began to handcuff him but had to dive out of the way at the last second when the younger brother, Dzhokhar Tsarnaev, drove a stolen car at them. They said the younger brother then ran over his brother's body as he drove away from the scene to escape.

Dzhokhar Tsarnaev is in a federal prison and faces a charge of using a weapon of mass destruction to kill.

The Tsarnaev brothers' mother says the allegations against them are lies.

Three of Dzhokhar Tsarnaev's friends, college classmates, were arrested and were accused of helping after the marathon bombing to remove a laptop and backpack from his dormitory room before the FBI searched it.

A top Republican senator on Thursday asked President Barack Obama's administration to explain how one of the students, who's from Kazakhstan, entered the United States without a valid student visa.

Sen. Chuck Grassley, R-Iowa, in a three-page letter to Department of Homeland Security Secretary Janet Napolitano, asked for additional details about the student visa applications for Azamat Tazhayakov and Dias Kadyrbayev, college roommates from Kazakhstan charged with obstruction of justice in the marathon bombing case, and how Tazhayakov was allowed to re-enter the United States in January.

Tazhayakov was a student at the University of Massachusetts Dartmouth when he left the country in December. In early January, his student visa status was terminated because he was academically dismissed by the university.

The third student arrested, Robel Phillipos, was charged with willfully making materially false statements to federal law enforcement officials during a terrorism investigation.

The lawyers for the Kazakh students said their clients had nothing to do with the bombing and were just as shocked by it as everyone else. Phillipos' attorney said the only allegation against him is "he made a misrepresentation."