Johnny Brady was serving a hospital order at St Andrew’s Healthcare in Billing Road, following convictions relating to serious assault and arson offences.
He absconded from the facility’s grounds around 3.30pm on Saturday, police said, and there have been no confirmed sightings of him since.
Members of the public should not approach him, said Northamptonshire Police on Sunday, and should instead report any sightings to the Force Control Room “as a matter of urgency” by calling 999.
Police are investigating three separate reports of bags of rubbish being set alight, which happened in the local area overnight and “may be linked to Johnny”.
He is described as white, about 5ft 9 and of a slim build, and was last seen wearing black Adidas tracksuit bottoms, a black hoodie, and black coloured trainers.
A second man also absconded from the St Andrew’s facility on Saturday, but was found by police overnight and “has been returned to the secure accommodation”.
Detective Superintendent Richard Tompkins said: “We have officers who are actively looking for Johnny however, he has now been missing for almost 24 hours, and with no confirmed sightings, we are becoming increasingly concerned.
“Johnny is serving a hospital order for convictions relating to arson and serious assault, which is why it is very important that the public do not approach him under any circumstances but should call 999 immediately.
“We are investigating three separate incidents of arson to bags of rubbish, which occurred overnight, in areas within a couple of miles of the hospital grounds which may be linked to Johnny.
“Arson has potentially fatal consequences and we therefore ask the public to be extra vigilant within their local communities. If you see anyone acting suspiciously near property or deliberately starting fires to items such as bins, please call us immediately on 999.”
Anyone who has seen Johnny or knows of his whereabouts is asked to call Northamptonshire Police on 999, quoting incident number 275 of 31/12/22.