A boxcar filled with nuclear waste from Colorado remained stranded here Saturday for the third day, monitored by armed guards, in a showdown over where to put the shipment.

Meanwhile, Blackfoot Mayor C. Dean Hill said the eastern Idaho community of some 10,000 people was not at all concerned about the boxcar filled with plutonium-contaminated garbage."I have not had one single person call me in concern about it," Hill said.

Gov. Cecil Andrus banned Wednesday the shipment of nuclear waste to the Idaho National Engineering Laboratory after the Energy Department could not say when a permanent waste storage site near Carlsbad, N.M. would open to accept nuclear waste stored at the INEL for nearly two decades.

"Promises from the DOE are no longer acceptable to me or the people of this state," Andrus said.

The shipment from the Rocky Flats, Colo., nuclear weapons plant was sent Wednesday to the INEL, but its progress was halted Thursday in Blackfoot.

Also Thursday, a shipment of nuclear waste headed for the INEL from the Argonne National Laboratory in Illinois was turned around in Wyoming and sent back when its driver was told Idaho State Police would stop it at the state line.

Andrus, who said he wants the shipment sent out of state, met Friday with Don Ofte, the Idaho manager for the DOE, and the two failed to resolve where the boxcar will go next.

"The shipment will stay in Blackfoot until we can work out a whole slew of questions," said Penny Phelps, a spokeswoman for the INEL.

Sending the boxcar back to Rocky Flats may cause more problems, Phelps said, because Colorado does not have a permit for long-term storage of such wastes.

Andrus' ban applies only to low-level and transuranic waste and does not affect shipments to the INEL from Three Mile Island in Pennsylvania or shipments of government-owned spent nuclear fuel processed at the INEL.

Rockwell International Inc., which operates Rocky Flats for the government, had planned to begin shipping plant wastes to the New Mexico facility this month. But the plant's opening has been delayed.

Some cities have attempted to set up nuclear-free zones but the federal government has pre-empted those moves, said Tom Bauman, a spokesman for the DOE.