Three high-profile black athletes have been sent racist mail that matches the hate letter sent to triple jumper Ashia Hansen.
The athletes, all members of Britain's Olympic team, opened the letters the day after a knife attack on Ms Hansen's white boyfriend last week.
Senior British athletes have been warned to be on their guard against further hate mail and police are screening mail sent to UK Athletics, the sports governing body. Police have told the three men to check if they are being followed.
Last week, Chris Cotter, a former long jumper aged 28, was wounded when he was stabbed in the back and slashed across the forehead by up to five men as he parked near Ms Hansen's home in Birmingham. One assailants had shouted racist abuse about his relationship, he said.
Tony Garbett, Superintendent of the West Midlands Police, said the letters had a Birmingham postmark. They had been addressed to UK Athletics and forwarded to the athletes' home addresses. "The content of these letters received by the athletes is the same [as that received by Ms Hansen]. We feel confident that they are linked," he said. "In broad terms, these letters refer to them representing Great Britain in the Sydney Olympics later this year."
Supt Garbett said they were "not threatening but are racist in nature" and that he was concerned that athletes who are out of the country preparing for the Games this autumn may return to similar racist mail.
Police have chosen not to identify the athletes. Unconfirmed reports suggested they included sprinter Dwain Chambers and high-jumper Ben Challenger.
Max Jones, the performance director of UK Athletics, said: "I think the three athletes will have been upset, but it's not going to change their routine or affect their training," he said. UK Athletics has sent a warning letter to its top athletes advising them to report to police any suspicious behaviour by people around them, even if it seemed trivial, he said.
Supt Garbett said the attack on Mr Cotter was being treated as attempted murder. He appealed for information about a dark Ford Sierra or Mondeo saloon car seen near Ms Hansen's house on the night of the stabbing.
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