Twenty-four people have been hospitalised, including one man in a serious condition, after a chemical spill at a Caltex oil refinery in east Brisbane.

Police said hydrogen fluoride, which when mixed with water becomes hydrofluoric acid, escaped when a pipe ruptured at the refinery in Lytton about 8.40am (AEST) on Thursday.

A total of 45 people were affected by the gas, which causes painful skin burns and breathing difficulties.

Queensland Ambulance spokesman John Bradbury told Channel Ten news their symptoms included shortness of breath, tightness in the chest and stinging chemical burns.

Twenty-one people were treated at the site but 24 were taken to four different Brisbane hospitals.

Caltex Lytton refinery manager Andrew Brewer said some of the people hospitalised were being kept in overnight for observation while others had already been released.

“None is in a critical condition,” he said.

Mr Brewer said people in the vicinity had reported a plume of gas emerging from the alkylation unit, prompting the evacuation of the refinery’s 700 employees and contractors.

He said the leaking unit had been immediately shut down and contained by a water deluge system.

Mr Brewer said hydrogen fluoride was used in the plant process for the manufacture of petrol.

“All of us at Caltex deeply regret that people have been injured at our site,” he said.

“Our focus today is on caring for the people affected and their families.”

Queensland Fire and Rescue Service spokesman Col Hartley said local residents were never in any danger from the toxic gas and its chemical by-product.

“The product did not leave the site so at no stage was the community or anybody in the immediate area at risk,” he told Channel Ten news.

Mr Brewer said as a mark of respect Caltex managing director and CEO Dave Reeves and Refining General Manager Eion Turnbull had also flown to Brisbane from Sydney on Thursday.

He said the families of those injured had been notified while a letter box of the area would inform local residents of the event.

Mr Brewer said Caltex would conduct a full investigation of the incident, which had not affected production at the refinery.