LAGOS, Nigeria (AP) — Gunmen have attacked a prison in southwest Nigeria, freeing dozens of inmates, an official told The Associated Press Saturday.

The third jailbreak in Africa’s most populous country this year raises more concerns about how safe detention facilities are in the West African nation where authorities have struggled to stem rising violence. A handful of security facilities, especially police stations, have been attacked in a similar manner in the past year.

Olanrewaju Anjorin, a spokesman of the Oyo correctional center in Oyo state, told the AP that the gunmen attacked the facility late Friday night and an investigation into the incident which will reveal the extent of damage has begun.

“I can’t ascertain the number of people that escaped or that were recaptured but I am telling you that the security has been beefed up around the custodial center and the town,” he told AP in a phone interview.

Francis Enobore of the Nigerian Prisons Service also confirmed the incident and said he was on his way to the attacked facility.

Friday’s attack is the third this year in Nigeria, where jailbreaks are becoming more frequent and police only capture a fraction of those who escape. Lagos-based online newspaper TheCable reported in July this year that at least 4,307 inmates had escaped from prisons since 2017, based on compiled media reports.

In 2021 alone, more than 2,000 inmates were freed in two earlier jailbreaks: on September 13 when 240 inmates were freed after gunmen attacked a detention facility in north-central Kogi state with explosives and on April 5 when at least 1,800 were freed in the southeast Imo state when another facility was also blown up.

Most of the recent jailbreaks in Nigeria seem not to be connected although the attacks are carried out in a similar manner with the use of explosives. Authorities have managed to rearrest some escaped inmates, sometimes in neighbouring states, while others return willingly.

A good number of those who have escaped in such attacks are yet to be convicted and still awaiting trial. Nigerian prisons hold 70,000 inmates but only about 20,000, or 27%, have been convicted, according to government data.