Detectives arrested a 26-year-old nurse on suspicion of murder over the deaths of three hospital patients given insulin-contaminated saline solution, British police said.

Rebecca Leighton worked at Stepping Hill Hospital in Stockport, where police were alerted last week to a batch of saline believed to have been deliberately tampered with.

Arrested ... nurse Rebecca Leighton.

The unexplained deaths of a 44-year-old woman and two men aged 84 and 71 are being linked to the contamination, while a fourth patient, a man in his 40s, remains critically ill.

"This morning, a 26-year-old woman was arrested on suspicion of murder. She remains in police custody for questioning. Inquiries are continuing," a spokesman for Greater Manchester Police said.