An inmate convicted of two murders and sentenced to two life terms escaped from a 153-year-old section of the Trenton state prison early Monday after burrowing out of his cell and using a handmade ladder to scale an outer wall, officials said.

Gonzalo Marrero, who would have to serve at least 60 years before being considered for parole, was spotted at 4 a.m. scaling the 20-foot wall at the prison by a tower guard, said Jim Stabile, spokesman for the state Department of Corrections.Stabile said Marrero, 37, jumped over the wall after the guard called out. Two other inmates who had also escaped from the cell - Jorge LaBrada and Andrew Bisesi, both 28 - did not try to escape after they heard the guard, he said.

The three were cellmates and burrowed through a 3-foot-thick wall to escape. They squeezed through a narrow opening into the prison compound, and then Marrero used a 19-foot ladder fashioned from wood scraps to scale the wall, Stabile said.

Marrero apparently cut himself on razor wire on the top of the wall because blood was found on the ladder and outside the prison, Stabile said.

Tracking dogs followed a trail of blood to a drainage system along Route 29, leading authorities to believe Marrero was still in the area.

Helicopters traveled up and down the river as authorities opened manholes and rifle-toting officers stood guard at street corners.