Dec. 14–A group of masked thieves has lifted ATMs from five Houston hotels in a week, including a heist during which one robber showed a machete to Marriott Hotel employees, police said.

Lt. Cathy Richards, of the Houston Police Department's robbery division, said the group has so far targeted ATMs that are not secured to floors or walls, allowing them to finish their heists in under three minutes.

Witnesses have said the group has ranged between four and eight men.

"These guys go straight in the front door and out the front door," she said at a press conference Thursday. "They target these hotels in the middle of the night when there is low visibility."

Richards said it's unclear how much cash has been in each ATM, and that the thieves are "just betting on there being something in there."

"What's unique about this group right here is that there are numerous of them," Richards said. "So I think with more of them, they feel a little bolder."

The latest robbery came around 1 a.m. Thursday when police said a group of men stormed the Marriott Hotel on JFK Boulevard. Police said a valet tried to yell at the group as they fled the lobby, after which one lifted his shirt and showed a machete.

It was the third robbery at a Marriott in as many days, and the first in which Richards said the thieves indicated that they had weapons. In other heists, she said they've only verbally threatened hotel employees — including telling one, "don't do anything and you'll get home tonight."

Around midnight Wednesday, about five to eight masked men raided a Courtyard by Marriott in west Houston, on Westheimer in the West Chase area.

Early Tuesday morning, a group of seven to ten men hit up a Galleria-area Marriott and sped away with the unbolted ATM in two Dodge Magnums and a Chevy Impala.

A Frontier Hotel on JFK Boulevard and a Double Tree Hotel on the Southwest Freeway were also robbed late last week, Richards said.

"It seems to be city-wide so far," she said.

Richards declined to list specific cars for citizens to look for, and warned citizens not to "do anything that would cause you to get hurt," should they be victims of robberies.

"Just be a really good witness," she said. "Cooperate with what their instructions are."

A spokeswoman for Marriott declined on Thursday to comment on details of the incidents, "as this is an active police investigation."

"We are grateful that no one was hurt in any of these incidents," company spokeswoman Hunter Hardinge said in an email. "We are working closely with local authorities and providing whatever assistance we can to aid them in apprehending those responsible for these crimes."