A man suspected of involvement in Monday's bank robbery in Sha Tin was arrested in Shenzhen before he was handed over to Hong Kong police.

A woman was also arrested on suspicion of assisting an offender.

Officers said the male suspect, 49, fled to Shenzhen through the Heung Yuen Wai Control Point after the robbery.

He was apprehended by mainland authorities on Tuesday and sent back to Hong Kong in the evening.

Officers also linked him to an attempted break-in in Tseung Kwan O earlier on Monday.

The female suspect, 34, was said to have helped the man escape.

She was arrested at a border checkpoint when she returned to Hong Kong on Tuesday.

“Our investigation revealed that the female suspect met with the male suspect shortly after the robbery. She accompanied him as he crossed into the mainland," superintendent Iu Wing-kan said in a media briefing.

"Since they accompanied each other throughout the entire journey to the mainland, there is a strong belief that she may have committed the offence of assisting an offender."

Police said cash equivalent to some HK$380,000 was taken in the robbery at a Hang Seng Bank branch in City One in Sha Tin, and a bank employee was injured.