The capital city’s Air Quality Index (AQI) was recorded at 43 and its fine particulate matter (PM 2.5) level at 10.5 µg/m3 at 10 a.m., placing its air quality in the ‘good’ classification, according to data gathered from 13 stations by Switzerland-based air quality monitoring facility IQAir AirVisual.

The AQI and PM 2.5 levels recorded the previous day were 156 and 112 µg/m3.

PAMAir, another air monitoring service based in Vietnam, also recorded AQI levels between 30 and 78 and PM 2.5 levels between 4.5 and 20.6 µg/m3 on Thursday morning, according to multiple monitoring stations in the city.

AQI level under 50 is considered ‘good’ and under 100 considered ‘moderate.’ PM 2.5 levels under 12 µg/m3 is considered ‘good’ and under 35.4 µg/m3 considered ‘moderate.’

Convective clouds are still forming over southern and eastern Hanoi, and are expected to bring more rain soon, the National Center for Hydro-Meteorological Forecasting said Thursday morning.

On Tuesday, authorities in Hanoi warned its people to limit outdoor activities because the air quality in the country has persistently been at unhealthy levels for days.

"Local people, especially children, the elderly, pregnant women and people with respiratory issues should refrain from traffic and outdoor activities," the government said in a statement.

Officials blamed the low quality of air in the capital on widespread construction activity, a growing number of cars and motorcycles on its roads and heavy industries, including steel works, cement factories and coal-fired plants.

The city of eight million people has more than five million motorbikes and 550,000 cars, and the number of private vehicles is increasing at a rate of 4.6 percent a year.