Police say that at around 6 pm, officerspolice received a report that a bin outside the hospital had been set on fire.
Police attended, along with the NIFRS, and the fire was extinguished.
Superintendent David Moore said: “Thankfully, no one was injured during the incident, which is being treated as arson at this time.
“Shortly after 11 am today a 23-year-old male was arrested on suspicion of arson endangering life with intent.
“The man currently remains in custody assisting police with their enquiries.
“I would ask anyone with any information about this incident to contact police in Lurgan on the non-emergency number 101, quoting reference number 1100 of 03/01/18.
“Alternatively, information can also be provided to the independent charity Crimestoppers on 0800 555 111 which is 100% anonymous and gives people the power to speak up and stop crime.”