The City of Ottawa is warning residents to beware of open sewers and maintenance holes after six more manhole covers have gone missing.

The thefts come after police charged a man with stealing 25 manhole covers last Friday.

The City says about 150 manhole covers have gone missing in the last month - 80 of which were stolen in one week.

A recycled, cast-iron manhole cover is worth about $50 and it is believed the covers are being stolen to sell for scrap metal.

Anyone who sees an open maintenance hole is advised to call the City's 311 hotline immediately.