SPRINGFIELD, Mo. -- City police released new pictures on Wednesday of men who committed four armed robberies at three area Walgreen's pharmacies.  Springfield detectives are working with Nixa detectives to solve four separate cases.

With each pharmacy robbery, investigators add yet another piece to the puzzle.  They said the latest hit, Tuesday in Nixa, matches up nearly exactly with three armed robberies in the Queen City.

"Similar movements, actions, things like that you look for in video," said Springfield Police Lt. Tad Peters.

Police watch each video frame by frame.  Each time, they said, the robber forced store employees back to the pharmacy, demanding a specific list of prescription drugs.

"The people seem to know exactly what type of drug they want when they go in," Peters said.

Police developed two separate descriptions of the robbers for the four pharmacy holdups.  The man they describe as the first robber is shown in surveillance pictures from the first robbery, Oct. 24 at the Walgreen's on South Campbell Avenue at Battlefield Road in Springfield, and again at the Walgreen's on East Sunshine Street on Dec. 11.

"The description on that one was white male, 5-foot-7 to 5-foot-10, and 150 to 170 pounds," Peters said.

There is a second description for the man who committed the other two robberies.  Information gathered on the man seen in the holdup in Nixa matches the profile that Springfield police built for the man captured on camera in the holdup at the store on South Campbell on Nov. 12.

"The description there: white male, 6-foot-2 to 6-foot-3, 220 to 225 pounds," Peters said.

Police want people to look at images very closely.  They said they can do a lot with very small pieces of information.  Police want people to see if they recognize the clothes, if they remember someone they know being gone during late evening or early morning hours, or if they saw someone out and about during those dates and times who could match the descriptions.

"Obviously these people are in some type of desperate situation.  Whether they're under the influence of the drugs, or just trying to get new supply for later, either way it's putting people in a lot of danger," Peters said.

Police said even the smallest piece of information can be enough to crack the case.  They said there is a small chance all the men captured on camera could be different people.  If that's the case, it is also possible those people could all be working together. 

The main number of the Springfield Police Department is (417) 864-1810.  The number for the anonymous tip line is (417) 869-TIPS.  The Nixa Police Department's number is (417) 725-2510.