A relative of two PIA flight passengers said he spoke to his father on the phone after the plane landed at Stansted Airport.
Zohaib Sattar said his father Abdul told him there was "no warning or threat" before the flight was diverted.
Zohaib Sattar said: "They have taken two people off the plane and are checking the plane all over.
"The rest are just sat there waiting for further information.
"My father said there was no warning or threat, all of a sudden the plane just turned around".
More top news
Doctors say they cannot do anything for little Abigail Jones who was born with brain cancer and Down Syndrome so every moment is precious.
Cool spells of sunshine and some showery outbreaks through rest of today.
Did the tragic pictures of Aylan Kurdi dead on a Turkish beach prompt the latest government U-turn?