The state government has asked district collectors and SPs to crack the whip on stone crushers units, violating environment norms.

In a letter sent to the home and revenue and disaster management departments, forest secretary R K Sharma said many stone crushers units were still functioning, flouting the 'site' (where the units are located) criterion. It requires crusher units to be located 500 metre away from human habitations and 200 metre from national and state highways.