A "massive manhunt" has been launched after awaiting-trial prisoners escaped from Malmesbury prison on Friday.

The number of inmates who escaped from the facility was not immediately known.

Police from Malmesbury and neighbouring police stations along the west coast, with correctional services officials, launched the search for the prisoners on Friday afternoon.

“The search party comprising detectives, who are on foot and in vehicles, has already covered much ground with the rearrest of several escapees,” said a Western Cape police and correctional services statement.

Members of the public were advised not to try to apprehend the escapees but to contact Malmesbury's police commander on 082 469 0975 or Jonathan Bredenkamp from correctional services on 072 878 2685.

“As the search intensifies additional support will be summoned. Meanwhile, an investigation is under way to determine how the escape occurred,” read the statement.

Videos shared on Twitter showed police chasing prisoners in Malmesbury, while other videos purported to show prisoners being arrested in different suburbs.

Western Cape traffic chief Kenny Africa said he was aware of information that a light delivery vehicle was hijacked and that traffic officers were placed on high alert.

-TimesLIVE