The rapid response car and an ambulance were sent by South Central Ambulance Service to a house in Stranding Street, Eastleigh, Hampshire, at 5.30pm on Wednesday where they had been falsely informed someone inside was in cardiac arrest.
But as they arrived at the property, a series of items were thrown at them leaving the crews "extremely shaken".
Paul Jefferies, assistant director of operations at South Central Ambulance Service NHS Foundation Trust (SCAS), said: "Following an emergency 999 call received from a house in Eastleigh, we immediately sent a rapid response car and an ambulance to the address as we were informed someone inside the house was in cardiac arrest.
"Staff in the two vehicles that arrived at the property were met with a barrage of bricks, glass, plastic tables and chairs and other items which were being thrown at them from the upstairs windows of the property.
"The staff immediately requested assistance from Hampshire police who were required to help gain access to the property where it was confirmed there was no patient inside.
"Actions such as these can put other people's lives in danger as the original staff who were sent to this location, along with additional SCAS staff to provide them with support and check their physical and mental wellbeing, would have been unable to respond to patients in the local area who had dialled 999 with genuine emergencies around that time.
"Fortunately the staff involved, though extremely shaken, were uninjured and later able to continue their shifts.
"We are working closely with Hampshire Constabulary and will continue to assist their investigation."
A Hampshire police spokesman said: "A 13-year-old girl and a 14-year-old girl, both from Eastleigh, were arrested on suspicion of assault, cause of wasteful employment of police and use of threatening/abusive/insulting words/behaviour to cause harassment/alarm/distress.
"They remain in custody at this time."