LOWELL, Mass. (AP) -Four men have pleaded not guilty to charges of murder and armed robbery in the killing of a Lowell man earlier this month.

Prosecutors say 43-year-old Timothy Stairs was stabbed to death and robbed on the evening of January 11 on Fisher Street in Lowell.

The four Lowell men were arrested on Wednesday, each on charges of murder and armed robbery.

Middlesex District Attorney Gerry Leone identified them as 14-year-old Alexis Garcia, 15-year-old Matthew Cancel, 16-year-old Pablo Roman and 17-year-old Jose Pedraza.

They have been ordered held without bail. A pretrial conference is set for Feb. 25.