Police in a sleepy Dutch town braced Thursday for an invasion of party-goers after a teenager’s birthday invite on Facebook went viral, prompting thousands of replies. Officers in Haren near the northern city of Groningen were on high alert after the schoolgirl posted a message inviting friends to her 16th birthday party on Friday, but forgot to mark it as a private event. “She posted the invitation on Facebook and sent it to friends, who then sent it to other friends and soon it spread like wildfire across the Internet,” Groningen police spokeswoman Melanie Zwama told AFP. “Now thousands of people have indicated that they might be attending,” she said, adding: “We are taking extra measures, but what they are I’m not at liberty to tell you.” Dutch mass-market daily De Telegraaf reported that 24,000 people received the invitation, of whom 2,400 already responded that they would come to Haren, population 18,000, for the party. One site referred to Friday’s party as “Project X Haren”, counting down the seconds to the event and claiming 150,000 people have been invited. It also published the party’s address, adding “By all means bring some friends!” But police have posted on the same site: “This is an urgent call by police and the town council. Do not come to Haren on Friday night. Police are ready to stop any disorder.”