AN ALLEGED witness to an armed robbery at the United service station has been arrested by Warwick police.

An 18-year-old Warwick man was thought to be an innocent bystander when a United service station in Wallace St was robbed in February.

The man has now been arrested in relation to the armed robbery at another United store on Friday evening.

About 8.30pm on Friday night, two men entered the business at Helene St where one of them allegedly produced a knife and stole almost $600 in cash from the premises.

Warwick police apprehended the two men by Saturday morning.

Two men, aged 18 and 19, have been charged with separate offences after the 19-year-old had allegedly produced a weapon.

The 19-year-old man was charged with one count each of armed robbery and possession of a utensil.

The 18-year-old man is the alleged witness who had been shopping at the United store on Wallace St when it was robbed at gunpoint on February 12.

Security footage had shown that about 3am the door of the 24-hour service station was opened to the customer, shortly followed by a masked attacker holding what appeared to be a rifle.

The attacker had asked the customer to lie on the floor and then demanded cash and cigarettes from the service station attendant.

No charges had been made in relation to the earlier incident, but police investigations since allege the 18-year-old was an accomplice in the February attack.

Further investigations led to the arrest on Monday morning at Texas of the man alleged to have brandished a rifle in the first attack.

He appeared in the Warwick Magistrates Court on Monday morning charged with armed robbery and has been remanded in custody until his next appearance on June 15.

Detective Senior Constable Ryan Harmer of Warwick police said the man had admitted the firearm was loaded.

"The man arrested was an associate of the 18-year-old witness," Snr Const Harmer said.

"There were other clues that pointed us to him," he said. "The firearm had been loaded and was capable of being fired."

Snr Const Harmer said it was thought the men had used money allegedly stolen in the attacks to buy drugs.

Service station manager Harry Singh said he was pleased an arrest had been made.

"I'm pretty happy, it's good for the community," Mr Singh said.

"People should pay for it and learn a lesson from it."

"I just want to thank the Warwick police, they've done a good job and have been a really big help."

An 18-year-old man has been charged with one count each of armed robbery in company in relation to alleged February and April attacks, and is due to appear in court on May 6.