A man has been arrested on suspicion of possessing explosive substances following an evacuation of three flats.
North Wales Police evacuated flats on Bron y Wern in Bagillt, Flintshire, after finding chemicals in a flat at about 05:30 GMT on Wednesday.
A bomb disposal unit was sent as a precaution, but police said it was not related to terrorism.
The force said there was no public risk and those who had to leave their homes have been allowed to return.
The man, in his 30s, was taken to hospital but has since been discharged and is due to be interviewed by police.
Supt Nick Evans said: "The incident was discovered by officers attending following concerns about a man's safety and they were fortunately alert enough to notice substances within the flat which caused them some concern.
"As a precaution, the adjoining flats were evacuated whilst other experts were summoned and the items were safely removed for a more comprehensive examination."