Story highlights Police: Mob attacked Christian couple Tuesday at the kiln where they worked

They were beaten and thrown into the burning kiln

Rights group calls it a "callous murder," indicates woman was pregnant

Blasphemy in Pakistan is punishable by death or life imprisonment

Pakistani police say they have arrested up to 40 people in connection with the killing of a Christian couple in Punjab province who were beaten, then pushed into a burning kiln after being accused of desecrating the Quran.

Local police officials said a mob from neighboring villages formed Tuesday after a local mullah declared the couple were guilty of blasphemy.

The mob allegedly marched to the couple's home, broke down their door, dragged them outside, beat them and threw them into the brick kiln where they both worked.

The attack happened in the town of Kot Radha Kishan, about 60 kilometers (37 miles) southwest of Lahore, the capital of Punjab. Police officials identified the woman as Shyman Bibi Urf Shamar, and her husband as Sajjad Nasir Zurjah Nazir Nasir.

The Human Rights Commission of Pakistan (HRCP), which dispatched a team to the scene, said in a statement that the couple had three young children -- two sons and a daughter, and indicated the slain woman was pregnant.

Photos: Rage, grief after killing of Christian couple Photos: Rage, grief after killing of Christian couple Rage, grief after killing of Christian couple – Relatives mourn the death of the couple, who were beaten and thrown into a kiln after allegedly desecrating the Quran in Kot Radha Kishan, Pakistan, November 5. Hide Caption 1 of 6 Photos: Rage, grief after killing of Christian couple Rage, grief after killing of Christian couple – Police identified the woman as Shyman Bibi Urf Shamar, and her husband as Sajjad Nasir Zurjah Nazir Nasir, seen here in this undated photo. Hide Caption 2 of 6 Photos: Rage, grief after killing of Christian couple Rage, grief after killing of Christian couple – Christians gather and pray for the couple after an act described as a "callous murder" by the Human Rights Commission of Pakistan (HRCP). Hide Caption 3 of 6 Photos: Rage, grief after killing of Christian couple Rage, grief after killing of Christian couple – Pakistan relatives pray at the site of the murder on November 5. The HRCP, said it appeared the incident stemmed from a dispute over money with the kiln's owners. It found no evidence that a Quran had been desecrated. Hide Caption 4 of 6 Photos: Rage, grief after killing of Christian couple Rage, grief after killing of Christian couple – Pakistani members of a committee investigate the killing. The accusation the couple had desecrated the Quran was announced via a mosque loudspeaker, the HRCP said. Hide Caption 5 of 6 Photos: Rage, grief after killing of Christian couple Rage, grief after killing of Christian couple – Pakistani Christians shout slogans to protest against the murder, which happened despite the presence of police. About four officers went to the site to urge the mob to give the couple up, but they were beaten up as well. Hide Caption 6 of 6

"HRCP is shocked and saddened beyond words by the callous murder of the couple and their unborn child," the group said.

According to the statement, the HRCP team "did not come across any evidence of desecration of the Holy Quran."

Desecration of the Quran is punishable by death or life imprisonment under Pakistan's anti-blasphemy law.

Human rights groups have long urged the country to repeal the law, arguing that it has led to discrimination, persecution and murder.

It is often used to settle personal vendettas, rights groups say, and people accused of the committing the crime are frequently targeted by mob violence

That, according to the HRCP, appeared to be the situation in Kot Radha Kishan, and that the incident stemmed with a dispute over money the kiln's owners said the couple owed them.

An accusation that the couple had desecrated the Quran "was spread to nearby villages and announcements [were] made through mosque loudspeakers," the HRCP said.

The mob that went to the kiln was estimated at around 500 people, the rights group said, citing local police.

The HRCP said its team learned that four policemen went to the kiln to demand that the couple be handed over for protection from the mob, but that the owners "instructed their employees not to hand the couple over and the policemen were also beaten up."

The kiln's owners were among those arrested, the rights group said, quoting police.