DENVER (AP) - The FBI joined the search Tuesday for an escaped Colorado prison inmate and authorities were considering expanding the search area.

Forty-eight-year-old Douglas J. Alward fled the maximum security Sterling Correction Facility on Sunday.

A Department of Corrections spokeswoman said authorities have been going door-to-door in towns and rural areas near Sterling in their search for Alward.

He was serving a 20- to- 40-year sentence for attempted murder, assault, burglary and kidnapping. Alward is considered extremely dangerous.

He had three previous escapes that involved kidnappings and a shootout with police.