An inspector from the Health & Safety Executive has contacted Tarmac at its Bayston Hill Quarry, near Shrewsbury, after the HSE received two reports of misfires at the site on November 11 and 17.
Bayston Hill Quarry, in Sharpstone Lane, supplies aggregates to customers in the Shrewsbury area.
A spokesman for Tarmac said: "We are aware of an isolated issue regarding misfired detonation materials at our Bayston Hill Quarry.
“Investigations have been underway since then, with senior managers and our health and safety team involved. The safety of employees is our main priority and changes have already been made to prevent a recurrence, working in full cooperation with the Health & Safety Executive.”
The Tarmac spokesperson said detonation materials are used routinely in the extraction of aggregates.
A spokesman for the Health & Safety Executive said: "HSE received two reports of misfires at Bayston Hill Quarry on November 11 and 17, 2021.
“An inspector contacted the company to ensure safety measures were in place to check for misfired explosives in material during processing following these incidents.
“Additional remedial measures have been put in place by the company to prevent danger.”
The HSE said that "misfires happen".
They add: "It’s part of post blast procedure to check that all the explosives used for this activity have fired and personnel are trained to identify misfired explosives and take remedial action if any are discovered."