Patients were evacuated from a private medical clinic after a gas leak yesterday afternoon (Wednesday).
OSD Healthcare in Boundary Way, Hemel Hempstead was temporarily closed yesterday after what the firm described as a "major gas leak" in the local area.
A statement on the clinic's website added: "As a result of this, we have been advised to evacuate and close the clinic."
It reopened later that day.
Cadent Gas, which operate and maintain the gas distribution network in that area, said a service pipe had been damaged by a third party at about 1pm.
A spokesman said: "Engineers made the damaged pipe safe and completed repairs yesterday.
"We returned to switch the gas on today but found that the boiler would not relight. Customer's are advised to arrange a Gas Safe registered engineer to do this work as it is an internal fault."
Suspected gas escapes should be reported on 0800 111 999.