A drone crashed near school pupils taking part in a sports day, raising concerns about the unmanned devices being tested at an airport.
It crashed less than a mile from Penparc school in Aberporth, on Wednesday and it is believed to be the fifth involving tests with the devices.
The Watchkeeper drones are being tested at the nearby West Wales Airport in Ceredigion.
A Ministry of Defence (MoD) spokesman said an investigation was taking place.
Other drone crashes happened in 2009 and 2014, while two plunged into the sea in 2017.
The drone was recovered from a field near the airport on Friday by specialist teams who took it away on a lorry.
Melanie Davies, a parent who was at the school's sports day, said: "It's a great concern. My blood ran cold when I heard about it. I can't believe they're allowed to do it."
An MoD spokesman said: "We are aware of an incident involving a Watchkeeper aircraft which did not result in any injuries. The aircraft has been secured and there is no risk to the public."
He confirmed there was no prohibition on flying over schools in the designated testing area.
The International Fellowship of Reconciliation in Wales is a campaign group that has protested against the testing of drones in the area.
Chairwoman Mererid Hopwood said: "One is dubious that perhaps, safe or unsafe, there is a feeling that it's ok to fly them over west Wales and it's not. Not here, not anywhere."
Ceredigion council said it "was not appropriate to make a comment without being fully aware of all the facts".