Mangalore Refinery and Petrochemicals Ltd (MRPL) saw its shares tumble 5% after an explosion struck the company's plant at Mangaluru, with thick smoke seen rising from a refinery unit at the site, The Economic Times reported.

The share-price slide came as the first market verdict on the incident. Investors reacted to visuals from the complex showing heavy smoke, and trading in the stock turned sharply negative on the day the news broke.

What happened at the Mangaluru complex?

An explosion occurred at MRPL's Mangaluru plant, according to the report. Witnesses and footage from the site showed thick smoke emanating from a refinery unit. The Economic Times did not report details on the cause of the blast, the specific unit involved, or the extent of any damage to process equipment.

MRPL operates its refining and petrochemical operations at the Mangaluru complex on India's west coast. The reported incident involved a unit within that refinery, and the visible smoke plume pointed to an ongoing or recent fire at the facility at the time the footage was captured.

How did the market respond?

The immediate market reaction was unambiguous. MRPL shares dropped 5% as news of the explosion and the images of smoke from the refinery unit circulated, The Economic Times reported.

A single-day decline of that size signals that investors priced in operational risk at the complex before the company or regulators provided a fuller account of the incident. Refinery accidents routinely trigger this pattern: the equity move arrives first, the damage assessment follows.

What is still unknown?

Several material questions remain open following the initial report:

• The unit where the explosion occurred and its role in the refinery's operations
• Whether the blast halted throughput or forced a shutdown of affected process units
• Any injuries among workers or contractors at the site
• The cause of the explosion — equipment failure, process upset, or another factor
• The timeline for any investigation by the company or safety regulators

The Economic Times report focused on the share-price fall and the visuals from the plant. It carried no casualty figures and no statement on production impact.

Why refinery incidents move shares this fast?

For a refining company, an explosion touches the three variables that drive earnings: run rates, turnaround schedules, and safety-compliance costs. Until MRPL quantifies the damage, the market trades on the worst visible signal — smoke from an operating unit — and the 5% discount reflects that uncertainty.

India's refining sector has built a strong safety record at its major complexes, but incidents at any site draw immediate scrutiny from regulators, insurers, and equity analysts alike. A damage assessment at Mangaluru will determine whether the event registers as a contained unit-level issue or a broader operational setback.

The watch item

The next signal is MRPL's own statement. Watch for a company disclosure on the affected unit, any production impact, and the expected timeline for restoration — the items that will determine whether the 5% share-price drop marks the bottom or the start of a longer reassessment of the complex's availability.