It's a wake up call for all those busy working at odd hours in offices -- working in night shifts can cause cancer by disrupting your body clock.

According to a new study, night shift work increases the risk of cancer by disrupting the circadian rhythm (body clock).

The report comes from a team of 44 scientists in 10 countries commissioned by the World Health Organisation's International Agency on Cancer Research, the WebMD reported.

The scientists noted that night shift work may raise cancer risk by suppressing production of melatonin, a chemical involved in the circadian rhythm.

They report "limited" evidence of a connection between cancer and night shift work in people.

The evidence included a higher rate of breast cancer in nurses who work in night shifts.

But those studies, which were observational, don't prove cause and effect. Many genetic and environmental factors affect cancer risk.

So the scientists also reviewed studies in which animals were exposed to light at night, disrupting the animals' body clocks.

Those studies provided "sufficient evidence" of a connection between circadian rhythm disruption and cancer, states the report.

The scientists concluded that "shift work that involves circadian rhythm disruption is probably carcinogenic to humans."