At least 70 people have died in Lahore, Pakistan over the last three weeks after ingesting contaminated medicines manufactured by local pharmaceutical companies.

The victims were all heart patients at the Punjab Institute of Cardiology.

The Pakistan Tribune newspaper reported that three drug factory owners -- Waseem Chaudhary, Tahir Azam and Chaudhary Nadir -- have been arrested in connection with the deaths and the ongoing investigation. More arrests are expected as Federal Interior Minister Rehman Malik has formed a committee to probe the tragedy.

Patients who took the sub-standard drugs endured a sudden drop of white cells and blood platelets and displayed symptoms similar to those of dengue fever -- a mosquito-borne illness quite common in Pakistan. However, when it was learned that all the dead were heart patients, suspicions pointed to the makers of the cardiovascular drugs.

Meanwhile, according to reports, a panic has spread in Lahore after health officials warned that as many as 40,000 people likely took the same contaminated medicines that caused the deaths.

Saeed Illahi, head of Punjab’s provincial health department, told the Agence France Presse news agency that more than 419 other heart patients in the Lahore area are already ill from taking the same drugs.

According to M Ilyas Khan, a BBC correspondent in Islamabad, the Pakistani pharmaceuticals market is extremely competitive, with local makers competing with large multo-national firms for coveted hospital contracts.