Cause of strong gas smell tracked down in Sumner

Fire crews have tracked down the cause of a mysterious gas smell reported in a Christchurch suburb this morning.

The Sumner and Woolston fire brigades were called to Evans Pass Rd about 3am on Monday after reports from people who could smell a strong gas odour.

A Fire and Emergency NZ spokeswoman said after a "very big drive around" fire crews found the smell was coming from a Christchurch City Council sewerage drain.

"It is not uncommonly mistaken for a gas smell...there was nothing we could do about that one."