Christmas gifts and cards were destroyed when arsonists torched the post box at Keighley Post Office on Wednesday night.

Burning tissues were thrust through the opening of the box located in the Towngate main building.

Police investigating the outbreak are treating it as arson and believe the attackers struck between 10.30pm and 10.45pm.

All the second-class mail, which included cards and presents, was destroyed in the blaze.

Fire Sub-officer Eddie Presland said: "There was a lot of damage done and most of the items burned out. It is particularly distressing at this time of year when people are sending gifts and cards to loved ones.

"We also noted quite a few videos had been sent, and they could have been of children's parties or family events. It will be very distressing for the people concerned that this has happened."

A Keighley police spokesman said someone deliberately pushed a burning substance through the letter box, and the incident was being treated as arson.

"The fact there was only minor damage to the building was more luck than anything else - the fire could have spread and caused much more serious damage," he said.

Four youths were seen in the area at the time, and officers are keen to speak to them, he said. All four are white, in their teens and between 5ft 6-5ft 8 tall.

One had short blond hair and was wearing a jumper with a white motif on the front and a white stripe halfway up each sleeve.

The other three all had short dark hair. One was wearing a grey jacket with a white collar and sleeves. Another wore a yellow jumper with stripes - possibly blue - around the chest, and a dark baseball cap. The fourth wore a dark jacket with a white hood and sleeves.

A Post Office spokesman said: "Any people who posted after the 6.30pm last collection and who are concerned about their mail should contact us. Any mail that can be recovered will either be forwarded or returned to the sender with a letter explaining what happened."

The letter box was temporarily out of order but the main office was open for business as usual. Anyone with information should telephone Keighley police on 01535 617085.