Officials in Rotterdam are warning parents to be very careful opening windows if young children live in the house, after five children fell to the ground in a string of accidents over the past month.

A three-year-old girl was the most recent child to fall, plunging three floors down after climbing up to a window. She is seriously ill in hospital.

“It is essential to think about how your furniture is arranged,” a police spokesman said. “What do you put in front of a window? Have you opened a window with blinds in front of it?”

The Dutch safety council Veiligheid NL said that there is always an increase in similar accidents during summer weather. “It is important to keep your eye on a child but it is also difficult to do so continuously,” a spokesman told broadcaster RTL. “And people often overestimate what a child understands of the rules or agreements you make with them.”

Parents should be particularly aware of giving children the opportunity to climb up to a window, the agency said.

None of the children who fell to the ground have died, but most are seriously ill in hospital. All five cases were accidents, police said.