A police cordon is in place outside a supermarket in Woodley following what officers described as a serious incident.
Emergency services were called to the car park outside the Iceland store on Crockhamwell Road on Saturday morning, with a large section of the area taped off by police.
Witnesses reported seeing a significant emergency response at the scene, while residents expressed shock at the presence of police vehicles and officers guarding the cordoned-off area.
Thames Valley Police has not yet released full details about the nature of the incident, but officers remain at the location while investigations continued.
People living nearby said they were surprised by the scale of the response in what is usually a busy shopping area.
Police have appealed for anyone who may have witnessed the incident or who has relevant information to come forward.
No further information about injuries or arrests has been released at this stage.
The cordon is expected to remain in place until investigators complete their work at the scene.
