ENGLEWOOD, Colo. - A letter carrier delivering mail late on Christmas Eve was robbed at knife-point.

Postal inspectors said the letter carrier was next to their postal vehicle at 6:40 p.m. when a man with a knife robbed the carrier.

It happened in the area of West Dartmouth Avenue and South Delaware Street in Englewood.

The carrier was working late trying to get everything out, according to U.S. Postal Inspector JoJan Henderson.

The male robber ran from the scene on foot. He was carrying something up against his chest as he ran off, Henderson said.

"This is pretty unusual, we don't get a lot of robberies," said Henderson.

Officials said they do not believe this robbery is connected to another letter carrier robbery in Denver on December 17.

That postal carrier was robbed by two men while delivering mail in the middle of the afternoon near East 22nd Avenue and Oneida  Street, U.S. Postal Inspector Pamela Durkey told 7NEWS.

The two robbers were armed with at least one knife, Durkey said.

One robber kept the worker busy while the second robber stole items from the back of a mail truck, Durkey said.

Officials said the robberies are being treated as separate investigations.

The U.S. Postal Inspection Service is asking for the public's help in identifying the person responsible for the robberies.  A reward of up to $50,000 is being offered for information leading to an arrest of the suspect or suspects.

If you have information about either incident, please call the U.S. Postal Inspection Service at 877-876-2455 (select Option 2).