Chief Minister H D Kumaraswamy said he has directed the authorities to suspend the services till the damaged portion was repaired.
"I am aware of the crack in a portion of the metro rail route. Technical experts on the subject have carried out an inspection. I have given a slew of directions.
One is that the metro rail services should be stopped because it should not cause any trouble to the public," Kumaraswamy told reporters in Belagavi.
The Bengaluru Metro Rail Corporation Limited (BMRCL) has raised a steel platform for the engineers to carry out tests.
It said the affected portion was small and would not affect the safety of the structure.
"The affected portion is very small and will not affect overall safety of the structure. The tests are being carried out as a matter of abundant precaution," said BMRCL ina statement.
The BMRCL said that it noticed a honeycomb in the concrete beam near Trinity Station.
"A more detailed inspection of concrete is required to be done through non-destructive methods to ensure that the concrete is adequately strong," the BMRCL said.
Regular Metro rail users and those frequently using the road beneath the elevated metro corridor expressed fears over the damage to the Metro pillar.
Vinay G, a resident living at Halasuru near the Trinity Circle said it was a cause for concern that the pillar developed a crack though initially authorities had said that the Metro elevated corridor was so strong that it would not require any maintenance for the next 25 years.