The recent explosion near the OIL well in Baghjan was caused by removing the spool during the blowout control operations.

To understand this, we need to know what a blowout is. A blowout is an uncontrolled release of oil or gas from a well. To control a blowout, a spool is often used. A spool is a device used to control the flow of fluids in and out of a well. During blowout control operations, the spool is an essential tool to manage the situation safely.

Option 2, the transfer of oil from its depot to the pipeline, is not the cause of the explosion in this case. Option 3, the leakage of methyl isocyanide, and option 4, the leakage of radiations from a radioactive substance, are not relevant to the explosion.

It is important to note that accurate information is crucial in situations like this, and any alert or clarification should be taken into consideration. Alert - The correct answer should be confirmed by official sources.