A new radio system at a south Wales police station has been tested after three officers and two civilian staff complained of feeling unwell.
Five staff at Barry station have said they felt unwell
The Tetra radio communication system has prompted protests from communities opposed to the masts.
02 Airwave said tests showed signal emissions at Barry were 1,600 times below health and safety guidelines.
Both Airwave and South Wales Police said there was no evidence the system was linked to the staff's ill health.
Two of Wales' four forces in Wales are using the new radio system which makes communication more secure and gives them greater coverage.
The Tetra system is expected to be fully up and running across the UK by spring 2005.
However the programme to provide a network of Tetra masts has met with opposition from people who claim the masts can make people ill.
The Chairman of the Police Federation in south Wales told BBC Wales that five staff members had complained of severe headaches, disrupted sleep patterns and dizziness.
Inspector David Hathway said: " Within south Wales we have had a number of officers in the Barry area who expressed concern that they felt unwell when they became aware that a Tetra mast was operating from that location.
"Obviously, those complaints will be part of the investigation as to the possible adverse effects of the use of this radio equipment."
Two of Wales' four police forces currently use the Tetra radio system
In a statement, 02 Airwave said: " We are aware of officer concern at the police station in Barry.
"O2 Airwave have been active in providing information to officers in Barry and taken emission level tests which show that radio frequency levels are at the very least 1,600 times below health and safety guidelines.
"The overwhelming scientific evidence concurs that there is no cause for concern.
"The latest research has reinforced the global scientific view that there is no evidence to support claims of ill health in relation to masts or handsets.
"What can be proved, however, is that the introduction of the Airwave system has already allowed the emergency services to save many lives here in the UK."
In a statement, South Wales Police said: "The Airwave system is a national one which is being rolled out across the country.
"Throughout its implementation in south Wales, we have said that we will look at any concerns raised - which we are doing.
"However, there is no evidence to suggest that the illnesses of these officers are linked to the system."
The Home Office, which is co-ordinating the Tetra system, have set up a health study to look at possible health concerns.
The south Wales force is one of those which will be shortly receiving health survey questionnaires.
But that study is expected to take as much as a decade.