Sydney firemen were reportedly unable to answer a call-out because their fire engine was being used by a firefighter to collect a pizza.
The pizza mission is said to have caused no danger to the public
"Apparently [he] decided to take the pumper to a pizza shop... for a bite to eat," an officer wrote in a letter obtained by local media.
The man concerned is then alleged to have met some friends and taken them for a ride in the fire engine.
He has been suspended on full pay, and an inquiry has been launched.
The incident is said to have taken place at the suburban Maroubra fire station.
Assistant Fire Commissioner John Benson told ABC radio that such a situation was "unheard of in the New South Wales Fire Brigade".
Mr Benson said there had been no danger to the public, because other fire brigades had responded to the call-out.
A spokesman for the state opposition Liberal Party, Andrew Humpherson, said the reports were "deeply alarming".
"This is about the public being able to be confident that an emergency service such as a fire brigade is able to respond to save lives and property... as a priority over pizzas."