HOUSTON -- A group of men is wanted in connection with at least 29 armed robberies of businesses throughout Houston, KPRC Local 2 reported Monday.

Houston police said the group has been targeting Hispanic-owned insurance and money transferring businesses. Most of the robberies have happened between 2 p.m. and 6 p.m. on Saturdays and Mondays, but they have also struck during other times the businesses are open.

The men, who normally operate in groups of two or three, walk into the businesses and pose as customers, police said.

Investigators said the men ask a few questions and then pull out guns. They order employees to get away from their desks and often tie them up or make them hide in another room, officials said.

"The suspects are always armed, and (in) a lot of the businesses, there's only one person working. Generally, it's been a female," said Colleen Nelson, an HPD Robbery investigator.

The men steal cash from the business and then flee, police said. Their average loot is between $200 and $1,000.

Police said as many as 20 people could be involved in the crime spree.

One of the targeted businesses was Amtex Auto Insurance in southwest Houston. It has since posted a sign that says "no cash."

The Amtex clerk said she was so terrified after the robbery that she quit after working there for 10 years.

None of the clerks suffered serious injuries, but police said they believe the robbers are becoming more violent.

The men were all described as Hispanic. Police said they often wear baseball caps, but they don't make any attempts to hide their faces. Several of them have spoken to their victims in Spanish with a Central American accent, officials said.

Anyone with information is asked to call the HPD Robbery Division at 713-308-0700 or Crime Stoppers at 713-222-TIPS.