MEDFORD, MA – McGlynn Middle School Principal Jake Edwards has been placed on paid administrative leave pending an investigation into the discovery of a gun magazine at the school that went unreported for weeks.

Medford Mayor Stephanie M. Burke said at a press conference Thursday she is "deeply concerned" that neither her nor Medford Police Chief Leo Sacco were informed of the Dec. 29 discovery until last Friday, Feb. 16. Burke said former Massachusetts Attorney General Martha Coakley, now a partner at the law firm Foley Hoag, will lead an independent investigation into the matter starting Friday. It will run separate from the school district's investigation.

Medford's schools are "safe," Sacco said Thursday. Seventeen law enforcement teams comprised of officers and K-9 units swept all schools Thursday to ensure a safe return from break for students next week. Anyone with information about the clip, which was loaded with "at least one bullet," to come forward.

Medford Superintendent Roy Belson has previously said he was wrong not to report the magazine to the mayor and police chief. It was found by a cleaning company in the McGlynn theater and turned over to the school custodian, who locked it in Edwards' office, according to Belson. It may have been thrown out the following day, Belson said. According to Burke, it is believed Belson knew about the discovery on Jan. 2.