SANTA FE, N.M. (AP) _ Authorities locked down New Mexico's largest prison and found a 30-foot tunnel in the basement after informants reported that inmates planned to riot and ``stab as many people as possible.''

``Inside the prison, when the gangs start getting together, of course they have a common goal,'' said Tim LeMaster, warden of the Penitentiary of New Mexico. ``In this case, I believe it was to create an incident in order for other people to escape.''

Gov. Gary Johnson declared an emergency Thursday and began preparations to ship 256 inmates to a prison in Arizona to relieve overcrowding.

Mike Toms, New Mexico Corrections Department spokesman, said today that things were ``pretty calm right now.'' He said the lockdown would probably last for several days.

As part of his declaration Thursday, the governor suspended a federal decree governing New Mexico prison conditions. The decree, which can be suspended in emergencies, was agreed to after 33 inmates were killed in a 1980 riot at the prison.

This time, inmate gangs were planning a riot in which they wanted to ``stab as many people as possible and kill everyone,'' LeMaster said in court documents filed with Johnson's declaration.

An informant at a state prison in Las Cruces, 280 miles away, said the riot was going to happen Wednesday night.

Acting on that information, other tips and concern over two months of increased violence among prisoners, authorities locked inmates in their cells early Wednesday and found weapons and the tunnel during a search of the three-building complex.

John Shanks, director of adult prisons, said the tunnel _ 30 to 35 feet long, 3 feet high and 3 feet wide _ was in the basement of the main prison near a laundry.

The tunnel would have had to extend at least another 30 feet to reach outside the main building, although even that would have been within the double fence surrounding the penitentiary.

Authorities also found a makeshift kitchen near the tunnel with some food, a gallon of gasoline and some paint. Authorities said they didn't know who knocked through a concrete wall and dug the tunnel or how long it had been under construction. Dirt on the floor was relatively fresh.

Up to 18 inmates normally had access to the area. The ``inmates were pretty much in control of that area, which greatly concerns us,'' Shanks said.

Prison officials said there had been 33 assaults on staff members, 34 assaults on inmates and 44 homemade knives found at the prison since early December _ numbers they said were higher than usual.

The penitentiary's main unit, where the tunnel was found, holds 420 inmates, but authorities consider 398 the maximum for safe operation.

At the Legislature, Speaker Raymond Sanchez said the House would quickly push through legislation to give corrections officials the authority to immediately move inmates to other states.

But Democrats, who hold both House and Senate majorities, suggested the Republican governor might be using the situation to pressure lawmakers into approving his prison proposals.

A Johnson spokesman, Dan Hill, said the administration ``will take great exception to any reference that this is some type of political situation.

``We have a critical, serious issue happening here that involves the public safety.''